tasks a-s
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Ingy döt Net
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12433 changed files with 156208 additions and 123 deletions
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/*REXX pgm converts infix arith. expressions to Reverse Polish notation.*/
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parse arg x; if x='' then x = '3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3'; ox=x
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showSteps=1 /*set to 0 (zero) if working steps not wanted.*/
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x='(' space(x) ') '; tokens=words(x) /*force stacking for expression. */
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do i=1 for tokens; @.i=word(x,i); end /*i*/ /*assign input tokens*/
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L=max(20,length(x)) /*use 20 for the min show width. */
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say 'token' center('input',L,'─') center('stack',L%2,'─') center('output',L,'─') center('action',L,'─')
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pad=left('',5); op=')(-+/*^'; rOp=substr(op,3); p.=; s.=; n=length(op); RPN=; stack=
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do i=1 for n; _=substr(op,i,1); s._=(i+1)%2; p._=s._+(i==n); end /*i*/
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/*[↑] assign operator priorities.*/
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do #=1 for tokens; ?=@.# /*process each token from @. list*/
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select /*@.# is: (, operator, ), operand*/
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when ?=='(' then do; stack='(' stack; call show 'moving' ? "──► stack"; end
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when isOp(?) then do /*is token an operator?*/
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!=word(stack,1) /*get token from stack.*/
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do while !\==')' & s.!>=p.?; RPN=RPN ! /*add*/
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stack=subword(stack,2); /*del token from stack.*/
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call show 'unstacking:' !
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!=word(stack,1) /*get token from stack.*/
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end /*while ···)*/
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stack=? stack /*add token to stack.*/
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call show 'moving' ? "──► stack"
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end
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when ?==')' then do; !=word(stack,1) /*get token from stack.*/
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do while !\=='('; RPN=RPN ! /*add to RPN.*/
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stack=subword(stack,2) /*del token from stack.*/
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!=word(stack,1) /*get token from stack.*/
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call show 'moving stack' ! '──► RPN'
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end /*while ···( */
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stack=subword(stack,2) /*del token from stack.*/
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call show 'deleting ( from the stack'
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end
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otherwise RPN=RPN ? /*add operand to RPN. */
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call show 'moving' ? '──► RPN'
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end /*select*/
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end /*#*/
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RPN=space(RPN stack)
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say; say 'input:' ox; say 'RPN──►' RPN /*show input and the RPN.*/
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parse source upper . y . /*invoked via C.L. or REXX pgm?*/
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if y=='COMMAND' then exit /*stick a fork in it, we're done.*/
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else return RPN /*return RPN to invoker (RESULT).*/
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/*──────────────────────────────────ISOP subroutine─────────────────────*/
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isOp: return pos(arg(1),rOp)\==0 /*is argument1 a "real" operator?*/
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/*──────────────────────────────────SHOW subroutine─────────────────────*/
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show: if showSteps then say center(?,length(pad)) left(subword(x,#),L),
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left(stack,L%2) left(space(RPN),L) arg(1); return
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@ -0,0 +1,57 @@
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/*REXX pgm converts infix arith. expressions to Reverse Polish notation.*/
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parse arg x; if x='' then x = '3 + 4 * 2 / ( ( 1 - 5 ) ) ^ 2 ^ 3'; ox=x
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g=0 /* G is a counter of ( and ) */
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do p=1 for words(x); _=word(x,p) /*catches unbalanced () and )( */
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if _=='(' then g=g+1
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else if _==')' then do; g=g-1; if g<0 then g=-1e9; end
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end /*p*/
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good=(g==0) /*indicate expression is good | ¬*/
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showSteps=1 /* 0: action steps not wanted.*/
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x='(' space(x) ') '; tokens=words(x) /*force stacking for expression. */
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do i=1 for tokens; @.i=word(x,i); end /*i*/ /*assign input tokens*/
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L=max(20,length(x)) /*use 20 for the min show width. */
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if good then say 'token' center('input' ,L,'─') center('stack' ,L%2,'─'),
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center('output',L,'─') center('action',L ,'─')
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pad=left('',5); op=')(-+/*^'; rOp=substr(op,3); stack=
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p.=; n=length(op); s.=; RPN=
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do i=1 for n; _=substr(op,i,1); s._=(i+1)%2; p._=s._+(i==n); end /*i*/
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/*[↑] assign operator priorities.*/
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do #=1 for tokens*good; ?=@.# /*process each token from @. list*/
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select /*@.# is: (, operator, ), operand*/
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when ?=='(' then do; stack='(' stack; call show 'moving' ? "──► stack"; end
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when isOp(?) then do /*is token an operator?*/
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!=word(stack,1) /*get token from stack.*/
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do while !\==')' & s.!>=p.?; RPN=RPN ! /*add*/
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stack=subword(stack,2); /*del token from stack.*/
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call show 'unstacking:' !
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!=word(stack,1) /*get token from stack.*/
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end /*while ···)*/
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stack=? stack /*add token to stack.*/
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call show 'moving' ? "──► stack"
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end
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when ?==')' then do; !=word(stack,1) /*get token from stack.*/
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do while !\=='('; RPN=RPN ! /*add to RPN.*/
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stack=subword(stack,2) /*del token from stack.*/
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!=word(stack,1) /*get token from stack.*/
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call show 'moving stack' ! '──► RPN'
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end /*while ···( */
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stack=subword(stack,2) /*del token from stack.*/
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call show 'deleting ( from the stack'
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end
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otherwise RPN=RPN ? /*add operand to RPN. */
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call show 'moving' ? '──► RPN'
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end /*select*/
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end /*#*/
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RPN=space(RPN stack)
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if \good then RPN = '─────── error in expression ───────'
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say; say ' input:' ox; say ' RPN──►' RPN /*show input and the RPN.*/
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parse source upper . y . /*invoked via C.L. or REXX pgm?*/
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if y=='COMMAND' then exit /*stick a fork in it, we're done.*/
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else return RPN /*return RPN to invoker (RESULT).*/
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/*──────────────────────────────────ISOP subroutine─────────────────────*/
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isOp: return pos(arg(1),rOp)\==0 /*is argument1 a "real" operator?*/
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/*──────────────────────────────────SHOW subroutine─────────────────────*/
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show: if showSteps then say center(?,length(pad)) left(subword(x,#),L),
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left(stack,L%2) left(space(RPN),L) arg(1); return
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