CS-Notes/docs/_style/prism-master/examples/prism-pure.html

<h2>Comments</h2>
<pre><code>#! shebang
// Single line comment
/* Multi-line
comment */</code></pre>

<h2>Strings</h2>
<pre><code>"This is a string."
"This is a string with \"quotes\" in it."</code></pre>

<h2>Numbers</h2>
<pre><code>4711
4711L
1.2e-3
.14
1000
0x3e8
01750
0b1111101000
inf
nan</code></pre>

<h2>Inline code</h2>
<p>Inline code requires the desired language to be loaded.
On this page, check C, C++ and Fortran <strong>before</strong> checking Pure should make
the examples below work properly.</p>
<pre><code>%<
int mygcd(int x, int y)
{
  if (y == 0)
    return x;
  else
    return mygcd(y, x%y);
}
%>

%< -*- Fortran90 -*-
function fact(n) result(p)
  integer n, p
  p = 1
  do i = 1, n
     p = p*i
  end do
end function fact
%>

%< -*- C++ -*-

#include &lt;pure/runtime.h>
#include &lt;string>
#include &lt;map>

// An STL map mapping strings to Pure expressions.

using namespace std;
typedef map&lt;string,pure_expr*> exprmap;

// Since we can't directly deal with C++ classes in Pure, provide some C
// functions to create, destroy and manipulate these objects.

extern "C" exprmap *map_create()
{
  return new exprmap;
}

extern "C" void map_add(exprmap *m, const char *key, pure_expr *x)
{
  exprmap::iterator it = m->find(string(key));
  if (it != m->end()) pure_free(it->second);
  (*m)[key] = pure_new(x);
}

extern "C" void map_del(exprmap *m, const char *key)
{
  exprmap::iterator it = m->find(key);
  if (it != m->end()) {
    pure_free(it->second);
    m->erase(it);
  }
}

extern "C" pure_expr *map_get(exprmap *m, const char *key)
{
  exprmap::iterator it = m->find(key);
  return (it != m->end())?it->second:0;
}

extern "C" pure_expr *map_keys(exprmap *m)
{
  size_t i = 0, n = m->size();
  pure_expr **xs = new pure_expr*[n];
  for (exprmap::iterator it = m->begin(); it != m->end(); ++it)
    xs[i++] = pure_string_dup(it->first.c_str());
  pure_expr *x = pure_listv(n, xs);
  delete[] xs;
  return x;
}

extern "C" void map_destroy(exprmap *m)
{
  for (exprmap::iterator it = m->begin(); it != m->end(); ++it)
    pure_free(it->second);
  delete m;
}

%></code></pre>

<h2>Example</h2>
<pre><code>queens n       = catch reverse (search n 1 []) with
  search n i p = throw p if i>n;
               = void [search n (i+1) ((i,j):p) | j = 1..n; safe (i,j) p];
  safe (i,j) p = ~any (check (i,j)) p;
  check (i1,j1) (i2,j2)
               = i1==i2 || j1==j2 || i1+j1==i2+j2 || i1-j1==i2-j2;
end;</code></pre>