The goal of this project is to develop a command-line-based interpreter for programs written in the Simple programming language. Simple is a programming language similar to Java, but it supports a very limited number of data types, operators, and statement types, and the interpreter will enable users to define and interpret Simple programs.
In a nutshell, Simple supports only two data types, namely bool and int: Values of type bool include only true and false, while values of type int range between -99999 and 99999, both inclusive. That is, calculation results of int type that are larger than 99999 or smaller than -99999 are always rounded to 99999 and -99999, respectively. In total, 16 different operators, namely %, +, -, *, /, #, ~, >, >=, <, <=, ==, !=, &&, ||, and !, and seven types of statements, namely variable definitions, skips, assignments, conditionals, loops, prints, and blocks, are supported in Simple; Each statement in a Simple program is identified by a unique label, while each variable or expression is identified by a unique name.
-
Command: vardef lab typ varName expRef
Effect: Defines a new variable definition statement with a unique label lab. When this variable definition statement is executed, a variable with the unique name varName and of type typ is defined and initialized to the value of the expression reference expRef, where typ is either bool or int. An expression reference is either a literal, a variable name, or an expression name.
Example: vardef vardef1 int x 100
Note: All variable/expression names and statement labels in Simple programs are identifiers, which 1) may contain only English letters and digits, 2) cannot start with digits, and 3) may contain at most eight characters; int, bool, true, false, and all command names (e.g., vardef and execute) are Simple keywords, and they cannot be used as variable/expression names or statement labels.
-
Command: binexpr expName expRef1 bop expRef2
Effect: Defines a new binary expression with a unique name expName. The new expression’s left operand is an expression reference expRef1, its binary operator is bop, and its right operand is an expression reference expRef2. The following 11 binary operators can be applied to int expression references: %, +, -, *, /, >, >=, <, <=, ==, !=; The following four binary operators can be applied to bool expression references: &&, ||, ==, and !=.
Example: binexpr exp1 x * 20
-
Command: unexpr expName uop expRef1
Effect: efines a new unary expression with a unique name expName. The new expression’s unary operator is uop, and its operand is an expression reference expRef1. The following two unary operators can be applied to int values: # and ~ (equivalent to unary + and - in Java). The following one unary operator can be applied to bool values: !.
Example: unexpr exp2 ~ exp1
-
Command: assign lab varName expRef
Effect: Defines a new assignment statement with a unique label lab. When this assignment statement is executed, the value of expression reference expRef will be assigned to the variable with name varName. The variable should have been defined by a vardef statement.
Example: assign assign1 x exp2
-
Command: print lab expRef
Effect: Defines a new print statement with a unique label lab. When this print statement is executed, the value of the expression reference expRef will be printed between a pair of square brackets.
Example: print print1 exp2
-
Command: skip lab
Effect: Defines a new skip statement with a unique label lab. When executed, a skip statement does nothing.
Example: skip skip1
-
Command: block lab statementLab1 ... statementLabn
Effect: Defines a new block statement with a unique label lab. The block statement contains a list of statements with labels statementLab1, ..., statementLabn (n > 0). When this block statement is executed, the statements in the block statement are executed in sequence.
Example: block block1 assign1 skip1
-
Command: if lab expRef statementLab1 statementLab2
Effect: Defines a new conditional statement with a unique label lab. When this conditional statement is executed, the statement with label statementLab1 is ex�ecuted if the expression reference expRef evaluates to true; Otherwise, the state�ment with label statementLab2 is executed.
Example: if if1 exp5 block1 print1
-
Command: while lab expRef statementLab1
Effect: Defines a new loop statement with a unique label lab. When this loop statement is executed, the value of the expression reference expRef is evaluated repeatedly: If it evaluates to true, the statement with label statementLab1 is executed; Otherwise, the loop terminates.
Example: while while1 true block1 (note that the statement with label block1 will be repeatedly executed for ever when this while statement is executed)
-
Command: program programName statementLab
Effect: Defines a new Simple program with a unique name programName, and the program has the statement labeled statementLab as its body. When the program is executed, the statement in its body is executed accordingly.
Example: program program1 while1
-
Command: execute programName
Effect: Executes the defined program named programName.
Example: execute program1
-
Command: list programName
Effect: Prints out the list of commands that defines the program with name programName.
Example: list program1
-
Command: store programName path
Effect: Stores the defined program with name programName into the file at path.
Example: store program1 d:\prog1.simple
-
Command: load path programName
Effect: Loads the defined program from path and names it as programName.
Example: load d:\prog1.simple program1
-
Command: quit
Effect: Terminates the execution of the interpreter.
-
Command: debug programName
Effect: Starts/Continues executing the program named programName in debug mode till completion or a breakpoint.
Example: debug program1
-
Command: togglebreakpoint programName statementLab
Effect: Sets/Removes a breakpoint at the statement labeled statementLab inside the program with name programName. During debugging, the execution of the program will suspend when encountering the breakpoint, i.e., the statement with label statementLab becomes the next statement to execute.
Example: togglebreakpoint program1 block1
-
Command: inspect programName varName
Effect: When the execution of program named programName is suspended during debugging, this command can be invoked to print out the value of the variable named varName within a pair of angle brackets, if the variable is in scope.
Example: inspect program1 x
-
Command: instrument programName statementLab pos expRef
Effect: Prints out the value of expRef in a pair of curly braces right before/after the statement with label statementLab from the program named programName is executed, where pos should be either before or after. Note that multiple instrument commands can be used to print out multiple strings at a single statement location.
Example: instrument program1 block1 after 5 will cause the interpreter toprint out “{5}” after each time the statement labeled block1 from program named program1 is executed.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent