compiling grass5.0beta4

[Kurt Gerber]

Hi 
I installed a new version of Linux (Suse 6.3) with linux 2.2.13. Now I tried to
recompile grass. 
When it comes to compile the different raster modules, compiling quits with an
error message, when trying to compile for example r.binfer, r.combine or
r.mapcalc. 
The error message says always, that the command 'lex' was not found.
Following the exact Error-output from compiling r.mapcalc:

#################################################################
/usr/src/grass5.0beta4/grass5.0beta/src/raster/r.mapcalc/polish
  mkdir OBJ.i686-linux-elf
  make -f OBJ.i686-linux-elf/make.rules
 
make[2]: Entering directory `/usr/src/grass5.0beta4/grass5.0beta/src/raster/r.mapcalc/polish'
rm -f lex.yy.c y.tab.c
rm -f OBJ.i686-linux-elf/main.o
gcc -g -O2   -I/usr/src/grass5.0beta4/grass5.0beta/src/include  -c main.c
mv main.o OBJ.i686-linux-elf/main.o
lex pol.l
make[2]: lex: Command not found
make[2]: *** [lex.yy.c] Error 127
make[2]: Leaving directory `/usr/src/grass5.0beta4/grass5.0beta/src/raster/r.mapcalc/polish'
make[1]: *** [all] Error 1
make[1]: Leaving directory `/usr/src/grass5.0beta4/grass5.0beta/src/raster/r.mapcalc'
GISGEN failure at STEP: src/raster/r.mapcalc
make: *** [do-install] Error 1  

Kurt Gerber