some arrows

catprog.tex

@@ -73,6 +73,8 @@
 \providecommand{\mto}{\mapsto}
 \providecommand{\xto}[1]{\,\xrightarrow{#1}\,}
 \providecommand{\xfrom}[1]{\,\xleftarrow{\;#1}\,}
+\providecommand{\To}{\mathrel{\Rightarrow}}			           % Double arrow
+\providecommand{\From}{\mathrel{\Leftarrow}}			         % Double arrow
 
 \providecommand{\dar}{\kern-1.2pt\operatorname{\downarrow}}	
 \providecommand{\uar}{\kern-1.2pt\operatorname{\uparrow}}