include the mbed library with this snippet

#include "mbed.h"

void Wave(void)
{
    int i = 0;
    //Preparazione dati
    Frequency = 1 / Frequency;
    Frequency /= 20;
    Frequency *= 1000000;  
    int T = (int)Frequency;
    float v = Amplitude / 3.3; 
    switch(Type)
    {
        case 1://sine wave
            v /= 2;
            T /= 20;
            while(i != 35)
            {
                for(float x = 0; x <= 1; x =+ 0.05)
                {
                    WaveForm = v * sin(x * 3.14159);
                    WaveForm =+ 0.5; 
                    wait_us(T);  
                }    
                i = Keys.read();   
            }
            break;
        case 2://Square wave
            int Ton;
            int Toff;
            Ton = (int)Frequency;
            Ton *= DutyCycle;  
            Toff = (int)Frequency - Ton;      
            while(i != 35)
            {
                WaveForm = v;
                wait_us(Ton);
                WaveForm = 0;
                wait_us(Toff);
                i = Keys.read();
            }
            break;
        case 3://Triangular wave
            v /= 2;
            T /= 80;
            while(i != 35)
            {
                for(float g = 0.5; g <= v; g =+ 0.05)
                {
                    WaveForm = g;
                    wait_us(T);
                }
                for(float a = v; a >= 0.5; a =- 0.05)
                {
                    WaveForm = a;
                    wait_us(T); 
                }
                for(float b = 0.5; b <= v - 0.5; b =- 0.05)
                {
                    WaveForm = b;
                    wait_us(T);
                }
                for(float c = v - 0.5; c <= 0.5; c =+ 0.05)
                {
                    WaveForm = c;
                    wait_us(T);
                }
                i = Keys.read();              
            }
            break;
        case 4://Saw tooth wave   
            v /= 2;
            T /= 40;
            while(i != 35)
            {
                 for(float y = 0.5; y <= v; y =+ 0.05)
                 {
                     WaveForm = y;
                     wait_us(T);
                 }    
                 for(float z = 0.5; z >= v - 0.5; z =- 0.05)
                 {
                     WaveForm = z;
                     wait_us(T); 
                 }       
                 i = Keys.read();     
            }
            break;
    } 
    return;
}