Improve how to redefine size in 1985/shapiro

Now one can just do:

    make clobber SIZE=5 alt

for example. This is done through a Makefile variable.

1985/shapiro/Makefile

@@ -58,7 +58,7 @@ ARCH=
 
 # Defines that are needed to compile
 #
-CDEFINE= -DC=39
+CDEFINE= -DC=${SIZE}
 
 # Include files that are needed to compile
 #
@@ -136,8 +136,11 @@ ${PROG}: ${PROG}.c
 alt: data ${ALT_TARGET}
 	@${TRUE}
 
+# variable to control size of maze for alt code
+SIZE=39
+
 ${PROG}.alt: ${PROG}.alt.c
-	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+	${CC} ${CFLAGS} -DC=${SIZE} $< -o $@ ${LDFLAGS}
 
 # data files
 #

1985/shapiro/README.md

@@ -5,7 +5,7 @@ make all
 ```
 
 There is alternate code which allows one to change the size of the maze. See
-[alternate code](#alternate-code) below.
+[Alternate code](#alternate-code) below.
 
 
 ### To run:
@@ -32,7 +32,7 @@ make alt
 If you wish to change the value you can do it like:
 
 ```sh
-make clobber CDEFINE="-DC=5" alt
+make clobber SIZE=5 alt
 ```
 
 Note that if it is not a number then obviously there will be a compilation

1985/shapiro/try.alt.sh

@@ -25,7 +25,8 @@ while ((i < 5)); do
     fi
 
     read -r -n 1 -p "Press any key to set to $C: "
-    make clobber CC="$CC" CDEFINE="-DC=$C" alt >/dev/null
+    echo 1>&2
+    make clobber CC="$CC" SIZE="$C" alt >/dev/null
     ./shapiro.alt
     ((i++))
 done
@@ -39,7 +40,7 @@ while :; do
     # ^-- 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
+	make clobber CC="$CC" SIZE="$REPLY" alt >/dev/null
 	./shapiro.alt
     else
 	exit 0