Data commit

Task/First-class-functions/Tcl/first-class-functions.tcl

@@ -0,0 +1,17 @@
+% namespace path tcl::mathfunc ;# to import functions like abs() etc.
+% proc cube x {expr {$x**3}}
+% proc croot x {expr {$x**(1/3.)}}
+% proc compose {f g} {list apply {{f g x} {{*}$f [{*}$g $x]}} $f $g}
+
+% compose abs cube          ;# returns a partial command, without argument
+apply {{f g x} {{*}$f [{*}$g $x]}} abs cube
+
+% {*}[compose abs cube] -3  ;# applies the partial command to argument -3
+27
+
+% set forward [compose [compose sin cos] cube] ;# omitting to print result
+% set backward [compose croot [compose acos asin]]
+% {*}$forward 0.5
+0.8372297964617733
+% {*}$backward [{*}$forward 0.5]
+0.5000000000000017