Add alt code to 1985/shapiro

This alt code allows one to resize the maze. Obviously if one uses -D
with a value that's not a number it will fail to compile. If it's <= 0
|| >= 5000 it will set to the default of 39.

The try.alt.sh script plays with this, first selecting a random number
(in range $RANDOM % 38) to compile with and then run. After that it runs
in an infinite loop, exiting only if input includes non-digit
characters. A value >= 5000 sets it to the default of 39 (in the code).

1985/shapiro/try.alt.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+#
+# try.alt.sh - demonstrate IOCCC winner 1985/shapiro alt code
+#
+
+# make sure CC is set so that when we do make CC="$CC" it isn't empty. Doing it
+# this way allows us to have the user specify a different compiler in an easy
+# way.
+if [[ -z "$CC" ]]; then
+    CC="cc"
+fi
+
+# run with default first
+make clobber CC="$CC" alt >/dev/null || exit 1
+./shapiro.alt
+
+i=0
+# while i < 5 randomly select a size and recompile it and run
+while ((i < 5)); do
+    # get random value in range RANDOM % 38. <=0 sets to 39 in the code but
+    # since 1 is kind of pointless so we set it to 2 if it's < 2.
+    C=$((RANDOM % 38))
+    if [[ "$C" -lt 2 ]]; then
+	C=2
+    fi
+
+    read -r -n 1 -p "Press any key to set to $C: "
+    make clobber CC="$CC" CDEFINE="-DC=$C" alt >/dev/null
+    ./shapiro.alt
+    ((i++))
+done
+
+# while input is only numbers recompile the alt code with that value.  If number
+# is <=0 it sets to 39 in the code but here if one enters a negative number it
+# will exit due to the '-'. 1 is rather pointless but we don't check for
+# it either.
+while :; do
+    read -r -p "Enter a value (any non-digit = quit): "
+    # ^-- SC2143 (style): Use grep -q instead of comparing output with [ -n .. ].
+    # shellcheck disable=SC2143
+    if [[ $(echo "$REPLY" | grep -E '\<[0-9]+\>') ]]; then
+	make clobber CC="$CC" CDEFINE="-DC=\"$REPLY\"" alt >/dev/null
+	./shapiro.alt
+    else
+	exit 0
+    fi
+done