Fun to Program – Language basics

TOC

This was originally written and created around 2013 and may require to be updated. (2021)

Language basics

See Wikipedia article on programing language.

Please note this may be inaccurate.

• statement
  • ; as statement terminator: C, C++, Java, Vala, …
  • ; as statement separator: Perl, Pascal, PL/I, SQL, …
  • EOL as statement terminator: Python
  • ; or EOL as statement terminator: Shell
  • ; as NOP statement: Lua
• block statement
  • { statement... } : C, C++, Java, Vala, Perl, Shell, Lua, …
  • BEGIN statement... END : Pascal
  • indented block : Python
• comment
  • /* ... */ or // ... : C, C++, Java, Vala
  • # ... : Perl, Python, Shell
  • -- ... or --[[ ... ]]: Lua (line and block comment)
• character constant
  • 'a': C, C++
• string
  • "abcdef" : C, C++, Vala, Python, Perl, Lua; Shell(subst)
  • 'abcdef' : Python, Perl, Lua; Shell(non-subst.)
  • """abcdef""" : Vala, Python (string literals that span multiple lines)
  • [==[abcdef]==] : Lua (string literals that span multiple lines)
• string concatenate operator
  • . : Perl
  • .. : Lua
  • + : Vala, Python, Pascal
  • put together side by side: Shell
  • call some function: C (think about glib)
• modulo
  • % : C, C++, Vala, Python, Perl, Lua
  • mod : Pascal
• floor
  • // : Python
  • div : Pascal
• power operator
  • ** : Python, Perl
  • ^ : Lua
  • use pow(...) function : C, C++, Vala
• bit not operator
  • ~ : C, C++, Vala, Python, Perl
• bit or operator:
  • | : C, C++, Vala, Python, Perl
• bit and operator:
  • & : C, C++, Vala, Python, Perl
• bit exclusive-or operator:
  • ^ : C, C++, Vala, Python, Perl
• logical not operator
  • ! : C, C++, Vala, Shell, Perl
  • not : Python, Lua
• logical or operator:
  • | : Python
  • || : C, C++, Vala, Perl, Shell
  • or : Lua
• logical or operator:
  • & : Python
  • && : C, C++, Vala, Perl, Shell
  • and : Lua
• if – triple choices as example
  • if (...) { statement... } else if (...) { statement... } else { statement... }` : C, C++, Vala, Java
  • if ...: statement... elif ...: statement... else: statement... : Python (multilined and indented)
  • if (...) { statement... } elsif (...) { statement... } else { statement... } : Perl
  • if ... then statement... elseif ... then statement... else statement... end : Lua
  • if [...]; then statement; ... elif [...] ; statement; ... else statement; ... fi : Shell
• for – indexed loop
  • for (i = 1; i <= n; i++) { statement... } : C, C++, Vala, Java
  • for i in range(1,n): statement... : Python (multilined and indented)
  • for ($i = 1; $i <= $n; $i++) { statement... } : Perl
  • for i=1, n, 1 do statement... end : Lua
• foreach – iterator loop
  • for (type &i : items) { statement... } : C++11
  • foreach (type i in items) { statement... } : Vala
  • for (type i : items) { statement... } : Java
  • for i in items: statement... : Python (multilined and indented)
  • foreach $i (@items) { statement... } : Perl
  • for i in items ... ; do statement; ... done : Shell
• while loop
  • while (loop_true) { statement... } : C, C++, Vala, Java, Perl
  • while loop_true: statement... : Python (multilined and indented)
  • while (loop_true) do statement... end : Lua
  • while [...]; do statement; ... done : Shell
• do while loop
  • do { statement... } while (loop_true) ; : C, C++, Vala, Java, Perl
  • while true: statement... if ! loop_true: break : Python (multilined and indented)
  • repeat statement... until ! loop_true : Lua
• break
  • supported : C, C++, Vala, Java, Python, Lua, Shell
  • Instead, use last: Perl
• continue
  • supported : C, C++, Vala, Java, Python, Shell
  • Instead, use next: Perl
  • NOT supported : Lua (Use if to skip the rest.)
• return
  • supported : C, C++, Vala, Java, Python, Lua, Shell
• multiple branching
  • switch(c) { case 'a': statement… break; default: statement... } : C, C++, Vala, Java
  • case $x in a) statement;... ;; ?) statement;... ;; esac : Shell
  • NOT supported. Use if ...: Perl, Python, Lua

Both return and exit are used for similar purposes for many languages.

• C : exit is a function in the libc library.
  • when exit is called, it terminates the process.
• C : return is a reserved keyword of the C language.
  • when return is in the main() function, it terminates the process.
  • when return is not in the main() function, it returns to the calling function code.
• Shell : exit is a builtin.
  • when exit is called, it terminates the shell code.
• Shell : return is a builtin.
  • when return is in the main shell code, it terminates the main shell code.
  • when return is in the block code { ...; }, it terminates the main shell code.
  • when return is in the subshell ( ...; ), it returns to the main shell code.
  • when return is in the sourced file, it returns to the sourcing shell code.

For the C++ language, you need to be careful uing exit in main() since no destructor will be called for the locally scoped objects for exit.