Initial data commit

Task/Execute-a-Markov-algorithm/Go/execute-a-markov-algorithm.go

@@ -0,0 +1,176 @@
+package main
+
+import (
+    "fmt"
+    "regexp"
+    "strings"
+)
+
+type testCase struct {
+    ruleSet, sample, output string
+}
+
+func main() {
+    fmt.Println("validating", len(testSet), "test cases")
+    var failures bool
+    for i, tc := range testSet {
+        if r, ok := interpret(tc.ruleSet, tc.sample); !ok {
+            fmt.Println("test", i+1, "invalid ruleset")
+            failures = true
+        } else if r != tc.output {
+            fmt.Printf("test %d: got %q, want %q\n", i+1, r, tc.output)
+            failures = true
+        }
+    }
+    if !failures {
+        fmt.Println("no failures")
+    }
+}
+
+func interpret(ruleset, input string) (string, bool) {
+    if rules, ok := parse(ruleset); ok {
+        return run(rules, input), true
+    }
+    return "", false
+}
+
+type rule struct {
+    pat  string
+    rep  string
+    term bool
+}
+
+var (
+    rxSet   = regexp.MustCompile(ruleSet)
+    rxEle   = regexp.MustCompile(ruleEle)
+    ruleSet = `(?m:^(?:` + ruleEle + `)*$)`
+    ruleEle = `(?:` + comment + `|` + ruleRe + `)\n+`
+    comment = `#.*`
+    ruleRe  = `(.*)` + ws + `->` + ws + `([.])?(.*)`
+    ws      = `[\t ]+`
+)
+
+func parse(rs string) ([]rule, bool) {
+    if !rxSet.MatchString(rs) {
+        return nil, false
+    }
+    x := rxEle.FindAllStringSubmatchIndex(rs, -1)
+    var rules []rule
+    for _, x := range x {
+        if x[2] > 0 {
+            rules = append(rules,
+                rule{pat: rs[x[2]:x[3]], term: x[4] > 0, rep: rs[x[6]:x[7]]})
+        }
+    }
+    return rules, true
+}
+
+func run(rules []rule, s string) string {
+step1:
+    for _, r := range rules {
+        if f := strings.Index(s, r.pat); f >= 0 {
+            s = s[:f] + r.rep + s[f+len(r.pat):]
+            if r.term {
+                return s
+            }
+            goto step1
+        }
+    }
+    return s
+}
+
+// text all cut and paste from RC task page
+var testSet = []testCase{
+    {`# This rules file is extracted from Wikipedia:
+# http://en.wikipedia.org/wiki/Markov_Algorithm
+A -> apple
+B -> bag
+S -> shop
+T -> the
+the shop -> my brother
+a never used -> .terminating rule
+`,
+        `I bought a B of As from T S.`,
+        `I bought a bag of apples from my brother.`,
+    },
+    {`# Slightly modified from the rules on Wikipedia
+A -> apple
+B -> bag
+S -> .shop
+T -> the
+the shop -> my brother
+a never used -> .terminating rule
+`,
+        `I bought a B of As from T S.`,
+        `I bought a bag of apples from T shop.`,
+    },
+    {`# BNF Syntax testing rules
+A -> apple
+WWWW -> with
+Bgage -> ->.*
+B -> bag
+->.* -> money
+W -> WW
+S -> .shop
+T -> the
+the shop -> my brother
+a never used -> .terminating rule
+`,
+        `I bought a B of As W my Bgage from T S.`,
+        `I bought a bag of apples with my money from T shop.`,
+    },
+    {`### Unary Multiplication Engine, for testing Markov Algorithm implementations
+### By Donal Fellows.
+# Unary addition engine
+_+1 -> _1+
+1+1 -> 11+
+# Pass for converting from the splitting of multiplication into ordinary
+# addition
+1! -> !1
+,! -> !+
+_! -> _
+# Unary multiplication by duplicating left side, right side times
+1*1 -> x,@y
+1x -> xX
+X, -> 1,1
+X1 -> 1X
+_x -> _X
+,x -> ,X
+y1 -> 1y
+y_ -> _
+# Next phase of applying
+1@1 -> x,@y
+1@_ -> @_
+,@_ -> !_
+++ -> +
+# Termination cleanup for addition
+_1 -> 1
+1+_ -> 1
+_+_ ->
+`,
+        `_1111*11111_`,
+        `11111111111111111111`,
+    },
+    {`# Turing machine: three-state busy beaver
+#
+# state A, symbol 0 => write 1, move right, new state B
+A0 -> 1B
+# state A, symbol 1 => write 1, move left, new state C
+0A1 -> C01
+1A1 -> C11
+# state B, symbol 0 => write 1, move left, new state A
+0B0 -> A01
+1B0 -> A11
+# state B, symbol 1 => write 1, move right, new state B
+B1 -> 1B
+# state C, symbol 0 => write 1, move left, new state B
+0C0 -> B01
+1C0 -> B11
+# state C, symbol 1 => write 1, move left, halt
+0C1 -> H01
+1C1 -> H11
+`,
+        `000000A000000`,
+        `00011H1111000`,
+    },
+}