Function composition: Difference between revisions

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 {{out}}
 <pre>$ patscc -O2 -DATS_MEMALLOC_GCBDW function_composition_2.dats -lgc && ./a.out
+.000000
+.000000</pre>
+One could even the composition procedures themselves be closures:
+<lang ats>#include "share/atspre_staload.hats"
+fn {t1, t2, t3 : t@ype}
+compose (f : t2 -<cloref1> t3,
+         g : t1 -<cloref1> t2) :<cloref1>
+    t1 -<cloref1> t3 =
+  lam x => f (g (x))
+fn
+compose_char2int2double
+          (f : int -<cloref1> double,
+           g : char -<cloref1> int) :<cloref1>
+    char -<cloref1> double =
+  compose<char, int, double> (f, g)
+implement
+main0 () =
+  let
+    val one_hundred = 100.0
+    val char_zero = '0'
+    val f = (lam y =<cloref1> add_double_int (one_hundred, y))
+    val g = (lam x =<cloref1> char2i x - char2i char_zero)
+    val z = compose_char2int2double (f, g) ('5')
+    val fg = compose_char2int2double (f, g)
+    val w = fg ('7')
+  in
+    println! (z : double);
+    println! (w : double)
+  end</lang>
+{{out}}
+<pre>$ patscc -O2 -DATS_MEMALLOC_GCBDW function_composition_3.dats -lgc && ./a.out
 .000000
 .000000</pre>