1 files changed, 34 insertions, 0 deletions
diff --git a/miralib/ex/polish.m b/miralib/ex/polish.m
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+||very simple testbed for Miranda unification package, "unify.m"
+
+||The expressions to be unified here are strings  written  in  (forward)
+||polish  notation,  such  as  "*+12-xy"  -  meaning  (1+2)*(x-y).   The
+||operators are + - * / with single letter variables, and  single  digit
+||constants.   We provide bindings for the free identifiers of "unify.m"
+||corresponding to this syntax.
+
+%include "unify.m"
+         { expr==[char]; operator==char; var==char;
+           isvar=isvar; getvar=getvar; putvar=putvar;
+           rator=rator; rands=rands; construct=construct;
+         }
+
+isvar e = letter (hd e)
+getvar = hd
+putvar = (:[])
+rator = hd
+rands (c:[]) = [], if digit c
+rands (c:e) = [a,b], if member "+-*/" c & e2=[]
+            = error "illegal string", otherwise
+              where 
+              (a,e1) = get e
+              (b,e2) = get e1
+              get [] = error "illegal string"
+              get (c:x) = ([c],x), if letter c \/ digit c
+                        = ([c]++a++b,x2), otherwise
+                          where
+                          (a,x1) = get x
+                          (b,x2) = get x1
+construct c xs = c:concat xs
+
+test = unifyexprs "*+x3/7x" "*+1y/z1" ||the result should be "*+13/71"
+test1 = unifyexprs "*+x3/7x" "*+1y/y1" ||not unifiable